@mixin fontsize($value, $size: "") {
    .fs-#{$size + $value} {
        font-size: #{$value}px;
    }
}

@mixin font-sizes() { // font-size 字号
    $font-size-list: 12, 14, 16, 18;
    @for $i from 1 through length($font-size-list) {
        @include fontsize(nth($font-size-list, $i));
    }
}